rnegbin {MASS} | R Documentation

## Simulate Negative Binomial Variates

### Description

Function to generate random outcomes from a Negative Binomial distribution, with mean `mu` and variance `mu + mu^2/theta`.

### Usage

    rnegbin(n, mu = n, theta = stop("theta must be given"))

### Arguments

`n` | If a scalar, the number of sample values required. If a vector, `length(n)` is the number required and `n` is used as the mean vector if `mu` is not specified.
`mu` | The vector of means. Short vectors are recycled.
`theta` | Vector of values of the `theta` parameter. Short vectors are recycled.

### Details

The function uses the representation of the Negative Binomial distribution as a continuous mixture of Poisson distributions with Gamma distributed means. Unlike `rnbinom` the index can be arbitrary.

### Value

Vector of random Negative Binomial variate values.

### Side Effects

Changes `.Random.seed` in the usual way.

### Examples

    # Negative Binomials with means fitted(fm) and theta = 4.5
    fm <- glm.nb(Days ~ ., data = quine)
    dummy <- rnegbin(fitted(fm), theta = 4.5)

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